Superconducting resonator to limit vertical connections in planar quantum devices

ABSTRACT

A set of superconducting devices is interconnected in a lattice that is fabricated in a single two-dimensional plane of fabrication such that a superconducting connection can only reach a first superconducting device in the set while remaining in the plane by crossing a component of a second superconducting device that is also located in the plane. A superconducting coupling device having a span and a clearance height is formed in the superconducting connection of the first superconducting device. A section of the superconducting coupling device is separated from the component of the second superconducting device by the clearance in a parallel plane. A potential of a first ground plane on a first side of the component is equalized with a second ground plane on a second side of the component using the superconducting coupling device.

TECHNICAL FIELD

The present invention relates generally to a superconductor device, afabrication method, and fabrication system for minimizing off-planeconnections in planar superconducting quantum devices. Moreparticularly, the present invention relates to a device, method, andsystem for superconducting resonator to limit vertical connections inplanar quantum devices.

BACKGROUND

Hereinafter, a “Q” prefix in a word of phrase is indicative of areference of that word or phrase in a quantum computing context unlessexpressly distinguished where used.

Molecules and subatomic particles follow the laws of quantum mechanics,a branch of physics that explores how the physical world works at themost fundamental levels. At this level, particles behave in strangeways, taking on more than one state at the same time, and interactingwith other particles that are very far away. Quantum computing harnessesthese quantum phenomena to process information.

The computers we use today are known as classical computers (alsoreferred to herein as “conventional” computers or conventional nodes, or“CN”). A conventional computer uses a conventional processor fabricatedusing semiconductor materials and technology, a semiconductor memory,and a magnetic or solid-state storage device, in what is known as a VonNeumann architecture. Particularly, the processors in conventionalcomputers are binary processors, i.e., operating on binary datarepresented in 1 and 0.

A quantum processor (q-processor) uses the odd nature of entangled qubitdevices (compactly referred to herein as “qubit,” plural “qubits”) toperform computational tasks. In the particular realms where quantummechanics operates, particles of matter can exist in multiplestates—such as an “on” state, an “off” state, and both “on” and “off”states simultaneously. Where binary computing using semiconductorprocessors is limited to using just the on and off states (equivalent to1 and 0 in binary code), a quantum processor harnesses these quantumstates of matter to output signals that are usable in data computing.

Conventional computers encode information in bits. Each bit can take thevalue of 1 or 0. These 1s and 0s act as on/off switches that ultimatelydrive computer functions. Quantum computers, on the other hand, arebased on qubits, which operate according to two key principles ofquantum physics: superposition and entanglement. Superposition meansthat each qubit can represent both a 1 and a 0 at the same time.Entanglement means that qubits in a superposition can be correlated witheach other in a non-classical way; that is, the state of one (whether itis a 1 or a 0 or both) can depend on the state of another, and thatthere is more information that can be ascertained about the two qubitswhen they are entangled than when they are treated individually.

Using these two principles, qubits operate as more sophisticatedprocessors of information, enabling quantum computers to function inways that allow them to solve difficult problems that are intractableusing conventional computers. IBM has successfully constructed anddemonstrated the operability of a quantum processor usingsuperconducting qubits (IBM is a registered trademark of InternationalBusiness Machines corporation in the United States and in othercountries.)

Superconducting devices such as qubits are fabricated usingsuperconducting and semiconductor materials in known semiconductorfabrication techniques. A superconducting device generally uses one ormore layers of different materials to implement the device propertiesand function. A layer of material can be superconductive, conductive,semi-conductive, insulating, resistive, inductive, capacitive, or haveany number of other properties. Different layers of materials may haveto be formed using different methods, given the nature of the material,the shape, size or placement of the material, other materials adjacentto the material, and many other considerations.

Superconducting devices are often planar, i.e., where the superconductorstructures are fabricated on one plane. A non-planar device is athree-dimensional (3D) device where some of the structures are formedabove or below a given plane of fabrication.

A q-processor is implemented as a set of more than one qubits. Thequbits are fabricated as a lattice of co-planar devices on a singlefabrication plane. Such an implementation of a q-processor is generallyaccepted as a fault-tolerant quantum architecture known as a SurfaceCode Scheme (SCS) or Surface Code Architecture (SCA).

FIG. 1 depicts an example Surface Code Architecture illustrating aproblem that can be solved using an illustrative embodiment.Superconducting qubit architectures such as SCA 100 arrange a number ofqubits 102 and 102A in a lattice formation in a single plane. The qubitsare coupled with each other using resonant lines 104 (also known as“bus”). The quantum state of a qubit 102 is read using read lines 106and 106A.

As can be seen, all resonant lines 104 are coplanar (in the same plane)with qubits 102 and 102A. As recognized by the illustrative embodiments,SCA 100 only allows coplanar read lines 106 to read qubits 102 that lieon the periphery of lattice 100. For qubits, such as qubit 102A, whichlie in an inside region of lattice 100, read line 106A has be connectedin a plane that is orthogonal to the plane of fabrication of lattice100. Suppose that the plane of fabrication is the two-dimensional XYplane according to the depicted coordinate axes. Read line 106A has tobe fabricated in Z direction, making the fabrication of SCA 100 athree-dimensional fabrication.

This manner of accessing a qubit (102A) for reading the qubit's quantumstate is known as “breaking the plane”. The illustrative embodimentsrecognize that breaking the plane due to the need of fabricatingnon-coplanar read lines (106A) to the non-peripheral qubits (102A) inlattice 100 leads to performance degradation in quantum statemeasurements, not be mention an increase in the complexity ofsuperconductor fabrication.

A non-peripheral region or area of a lattice is an area located inside aperimeter of the lattice. Generally, in the same plane as the area, theperimeter includes a device, wire, or circuit that will have to becrossed to reach a device located in the area.

A solution is needed such that superconducting devices located in thenon-peripheral areas of an SCA lattice can be attached to other circuitswithout breaking the plane. For example, such a solution would enablecoupling qubit 102A and other similarly situated superconducting devicesto a coplanar read line and other coplanar bondings on the chip orelsewhere on a circuit board, instead of having to fabricate read line106A and other similar non-coplanar structures.

SUMMARY

The illustrative embodiments provide a superconducting device, and amethod and system of fabrication therefor. A superconducting device ofan embodiment includes a set of superconducting devices interconnectedin a lattice, wherein the lattice is fabricated in a singletwo-dimensional plane of fabrication such that a superconductingconnection can only reach a first superconducting device in the setwhile remaining in the plane by crossing a component of a secondsuperconducting device that is also located in the plane. The embodimentfurther includes a superconducting coupler formed in the superconductingconnection of the first superconducting device, the superconductingcoupling device having a span and a clearance height, wherein a sectionof the superconducting coupling device is separated from the componentof the second superconducting device by the clearance in a parallelplane. The embodiment further includes a first ground plane on a firstside of the component, wherein the superconducting coupling deviceequalizes a potential of the first ground plane with a potential of asecond ground plane on a second side of the component. Thus, theembodiment provides a manner of fabricating a coplanar superconductingquantum processing circuit.

In another embodiment, the superconducting coupler comprises aresonator, and wherein the resonator is formed using a wirebond. Thus,the embodiment provides a particular manner of fabricating a coplanarline connecting to a non-peripherally located superconducting quantumprocessing device in a lattice of quantum processing devices.

In another embodiment, the superconducting coupler comprises aresonator, and wherein the resonator is formed using a coplanarwaveguide. Thus, the embodiment provides a different manner offabricating a coplanar line connecting to a non-peripherally locatedsuperconducting quantum processing device in a lattice of quantumprocessing devices.

Another embodiment further includes a ground plane coupling between thefirst ground plane and the second ground plane. Thus, the embodimentprovides a structure that equalizes the ground plane potential across acrossed component.

In another embodiment, the ground plane coupling is a superconductingcoupling. Thus, the embodiment provides a particular manner offabricating the structure that equalizes the ground plane potentialacross a crossed component.

In another embodiment, the ground plane coupling is a superconductingcoupling, wherein the superconducting coupler comprises asuperconducting resonator, and wherein a shape and a material of thesuperconducting resonator and the superconducting coupling are same as ashape and a material of the superconducting resonator. Thus, theembodiment provides a different manner of fabricating the structure thatequalizes the ground plane potential across a crossed component.

Another embodiment further includes a rising section of thesuperconducting coupler, wherein the rising section couples one end ofthe superconducting coupler to one section of the superconductingconnection on the first side of the component. The embodiment includes arejoining section of the superconducting coupler, wherein the rejoiningsection couples a second end of the superconducting coupler to thesecond section of the superconducting connection on an opposite side ofthe component. Thus, the embodiment provides a specific manner offabricating a coplanar line plane that is substantially parallel to aplane of fabrication of a non-peripherally located superconductingquantum processing device in a lattice of quantum processing devices.

In another embodiment, the clearance at least equals a thresholdclearance, and wherein an insulator is formed between the component andthe superconducting coupler to create the clearance. Thus, theembodiment provides a manner of electrically and magnetically separatingthe coplanar line connecting to a non-peripherally locatedsuperconducting quantum processing device, from a crossed component in alattice of quantum processing devices.

In another embodiment, the first superconducting device is a firstqubit, wherein the second superconducting device is a second qubit,wherein the superconducting connection of the first superconductingdevice is a read line of the first qubit, and wherein the component ofthe second superconducting device is a resonant line of the secondqubit. Thus, the embodiment provides a manner of fabricating a latticeof coplanar qubits without using 3D lines.

An embodiment includes a fabrication method for fabricating thesuperconducting device.

An embodiment includes a fabrication system for fabricating thesuperconducting device.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofthe illustrative embodiments when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 depicts a block diagram of a network of data processing systemsin which illustrative embodiments may be implemented;

FIG. 2 depicts a block diagram of a data processing system in whichillustrative embodiments may be implemented;

FIG. 3 depicts an example implementation of a coupling resonator inaccordance with an illustrative embodiment;

FIG. 4 depicts another example configuration of a coupling resonator inaccordance with an illustrative embodiment;

FIG. 5 depicts a simulation result from using a coupling resonator inaccordance with an illustrative embodiment;

FIG. 6 depicts another simulation result from using a coupling resonatorin accordance with an illustrative embodiment;

FIG. 7 depicts another simulation result from using a coupling resonatorin accordance with an illustrative embodiment; and

FIG. 8 depicts a set of equations to compute a number of jumps needed ina lattice in accordance with an illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments used to describe the invention generallyaddress and solve the above-described problems and other relatedproblems by providing a superconducting resonator to limit verticalconnections in planar quantum devices. The illustrative embodiments alsoprovide a fabrication method and system for fabricating asuperconducting resonator to limit vertical connections in planarquantum devices.

An embodiment provides a superconducting coupling device, which can beimplemented as superconducting wirebond, a coplanar waveguide (CPW), orsome combination thereof in superconducting quantum logic circuit. Asuperconducting coupling device formed in accordance with anillustrative embodiment operates as a resonator (hereinafter referred toas a “coupling resonator”).

A wirebond is a conductor formed using a bonding apparatus, to create asuperconductive join between two superconducting lines or between asuperconducting component and another component on the chip or circuitboard. In one embodiment, the wirebond has a round cross-section. Acoplanar waveguide is a type of superconducting planar transmission linedesigned to carry microwave-frequency signals.

Another embodiment provides fabrication method for the couplingresonator, such that the method can be implemented as a softwareapplication. The application implementing a fabrication methodembodiment can be configured to operate in conjunction with an existingsuperconducting fabrication system—such as a lithography system.

For the clarity of the description, and without implying any limitationthereto, the illustrative embodiments are described using an examplenumber of qubits arranged in a lattice. An embodiment can be implementedwith a different number of qubits, different arrangements in a lattice,a superconducting device other than a qubit, or some combinationthereof, within the scope of the illustrative embodiments. An embodimentcan be implemented to similarly improve other coplanar superconductingfabrications where a coupling to a superconducting element undesirablybreaks the plane.

Furthermore, a simplified diagram of the example coupling resonator isused in the figures and the illustrative embodiments. In an actualfabrication of a coupling resonator, additional structures that are notshown or described herein, or structures different from those shown anddescribed herein, may be present without departing the scope of theillustrative embodiments. Similarly, within the scope of theillustrative embodiments, a shown or described structure in the examplecoupling resonator may be fabricated differently to yield a similaroperation or result as described herein.

Differently shaded portions in the two-dimensional drawing of theexample structures, layers, and formations are intended to representdifferent structures, layers, materials, and formations in the examplefabrication, as described herein. The different structures, layers,materials, and formations may be fabricated using suitable materialsthat are known to those of ordinary skill in the art.

A specific shape, location, position, or dimension of a shape depictedherein is not intended to be limiting on the illustrative embodimentsunless such a characteristic is expressly described as a feature of anembodiment. The shape, location, position, dimension, or somecombination thereof, are chosen only for the clarity of the drawings andthe description and may have been exaggerated, minimized, or otherwisechanged from actual shape, location, position, or dimension that mightbe used in actual lithography to achieve an objective according to theillustrative embodiments.

Furthermore, the illustrative embodiments are described with respect toa specific actual or hypothetical superconducting device, e.g., a qubit,only as an example. The steps described by the various illustrativeembodiments can be adapted for fabricating a variety of planar couplingresonators in a similar manner, and such adaptations are contemplatedwithin the scope of the illustrative embodiments. A coupling resonatoris depicted as jumping over a single superconducting device only as anon-limiting example. From this disclosure, those of ordinary skill inthe art will be able to conceive and fabricate coupling resonators thatjump over more than one superconducting devices in a single jump, andsuch adaptations are contemplated within the scope of the illustrativeembodiments. Jumping over a device, in the manner a coupling resonatoris fabricated, is considered coplanar with the device even though thecoupling resonator follows a path that is elevated from the plane of thefabrication. The coupling resonator is regarded as coplanar because theelevated path is not substantially orthogonal to the plane offabrication but substantially parallel to the plane of fabrication in atleast one section of the coupling resonator and joins back to the planeof fabrication in at least two sections of the coupling resonator.

An embodiment when implemented in an application causes a fabricationprocess to perform certain steps as described herein. The steps of thefabrication process are depicted in the several figures. Not all stepsmay be necessary in a particular fabrication process. Some fabricationprocesses may implement the steps in different order, combine certainsteps, remove or replace certain steps, or perform some combination ofthese and other manipulations of steps, without departing the scope ofthe illustrative embodiments.

The illustrative embodiments are described with respect to certain typesof materials, electrical properties, structures, formations, layersorientations, directions, steps, operations, planes, dimensions,numerosity, data processing systems, environments, components, andapplications only as examples. Any specific manifestations of these andother similar artifacts are not intended to be limiting to theinvention. Any suitable manifestation of these and other similarartifacts can be selected within the scope of the illustrativeembodiments.

The illustrative embodiments are described using specific designs,architectures, layouts, schematics, and tools only as examples and arenot limiting to the illustrative embodiments. The illustrativeembodiments may be used in conjunction with other comparable orsimilarly purposed designs, architectures, layouts, schematics, andtools.

The examples in this disclosure are used only for the clarity of thedescription and are not limiting to the illustrative embodiments. Anyadvantages listed herein are only examples and are not intended to belimiting to the illustrative embodiments. Additional or differentadvantages may be realized by specific illustrative embodiments.Furthermore, a particular illustrative embodiment may have some, all, ornone of the advantages listed above.

With reference to FIG. 2, this figure depicts an example couplingresonator in accordance with an illustrative embodiment. Schematic view200 shows a portion of lattice 100 of FIG. 1, and includes animprovement imparted by an embodiment.

View 200 depicts a superconducting device, e.g., qubit 102A, that islocated in the non-peripheral area of lattice 100. As different fromlattice 100, where read line 106A is constructed in Z direction, anembodiment fabricates microwave signal transmission line 202 in the sameplane as the plane of qubit 102A (the aforementioned XY plane). In anon-limiting example, line 202 can be a substitute for read line 106A inFIG. 1, and can operate as read line 202 coupled to qubit 102A.

For coplanar fabrication, at or near an area in lattice 100 line 202 hasto cross another component (the crossed component) in the same plane, towit, the XY plane. In such an area, an embodiment fabricates couplingresonator 204. Coupling resonator 204 elevates above the plane bydeparting from the plane in one section (rising section 204A), runningsubstantially distant from (not necessarily parallel to) the plane inanother section (elevated section 204B), and rejoining the plane in athird section (rejoining section 204C). The embodiment positions one ormore sections 204A-C of coupling resonator 204 in such a way that atleast elevated section 204B jumps over the crossed component. Two ormore of sections 204A-C may be combined as a single section (see anexample in FIG. 2, diagram 200C).

Jumping over the crossed component means clearing or passing over thecrossed component by at least a threshold clearance. In one embodiment,the threshold clearance is at least equal to a distance beyond which amagnetic field created by the crossed component remains effectivelyundisturbed (is disturbed by a negligible amount) by a magnetic fieldcreated by the signals passing through the coupling resonator. In oneembodiment, the threshold clearance is a height of an insulatingstructure fabricated on the XY plane above the crossed component.

Coupling resonator 204 has a span. The span of the coupling resonator isthat length of the coupling resonator where every portion of that lengthis at least the threshold clearance distance away from the crossedcomponent. In one embodiment, the span includes the rising section 204A,elevated section 204B, and rejoining section 204C. In another embodimentthe span includes only elevated section 204B and does not include therising and the rejoining sections 204A and 204C, the difference being ina manner in which the rising and the rejoining sections 204A and 204Care fabricated. Some non-limiting example manners of fabricating thevarious sections of coupling resonator are depicted in schematicdiagrams 200A, 200B, and 200C in this figure.

After rejoining section 204C rejoins the plane, line 202 continues. Anynumber of coupling resonators 204 may be included in line 202 in asimilar manner. Different coupling resonators 204 in a given line 202may be formed differently from one another—some examples of the possibledifferences are shown in diagrams 200A, 200B, and 200C.

With reference to FIG. 3, this figure depicts an example implementationof a coupling resonator in accordance with an illustrative embodiment.View 300 depicts superconducting chip (or die) 302 in which one or moresuperconducting devices are fabricated in the XY plane as shown. Forexample, chip 302 may include lattice 100 from FIG. 1. Superconductingdevice 102A is qubit 102A in lattice 100. Line 202 may be a read linefor qubit 102A. Line 202 begins at qubit 102A, includes a non-limitingmanifestation of coupling resonator 204, and continues to a destination(not shown).

Only as a non-limiting example, coupling resonator 204 is depicted inFIG. 3 with a threshold clearance of 200 microns and a span of 1millimeter (mm). the length of line 202 before and after couplingresonator 204 is immaterial for the purposes of the illustrativeembodiments.

With reference to FIG. 4, this figure depicts another exampleconfiguration of a coupling resonator in accordance with an illustrativeembodiment. In configuration 400, qubits 102 and 102A participate inlattice 100 in the manner depicted in FIG. 1. Qubit 102A has line 202 asdescribed with respect to FIG. 3. Qubit 102 has line 402, which can be aresonant line 104 or a read line 106 associated with qubit 102,depending on the particular fabrication. Line 402 forms a crossedcomponent for coupling resonator 404. Coupling resonator 404 is anexample of coupling resonator 204 depicted in FIG. 3.

Lines 202 and 402 divide the fabrication plane into ground planes 406A,406B, 406C, and 406D as shown. The signal and potential (voltage) ofground planes (collectively referred to as “potential of ground plane”)across crossed component 402 has to be equalized. This equalization hasto be performed on either side of line 202 which includes couplingresonator 404. For example, the potential of ground plane 406A has to beequalized with the potential of ground plane 406B, and the potential ofground plane 406C has to be equalized with the potential of ground plane406D.

For equalization of ground plane potential in this manner, couplingresonator 404 includes additional superconducting couplings. In oneembodiment, superconducting coupling 408 is formed to equalize thepotential of ground planes 406A and 406B, and superconducting coupling410 is formed to equalize the potential of ground planes 406C and 406D.In one embodiment, couplings 408 and 410 are fabricated usingsubstantially the same method and materials as coupling resonator 404.

Couplings 408 and 410 can each include a rising section similar tosection 204A, an elevated section similar to section 204B, and arejoining section similar to section 204C. One or more of the risingsection, elevated section, and rejoining section of coupling 408 may becombined. Similarly, one or more of the rising section, elevatedsection, and rejoining section of coupling 410 may be combined.

While only four ground planes 406A-D are depicted, an implementationmight create more than four ground planes by laying out variouscomponents differently than shown. Accordingly, potential equalizationmay be needed across more than two pairs of ground planes. Couplingssimilar to couplings 408 and/or 410 can be fabricated in a mannerdescribed herein to equalize the potentials across as many ground planepairs as an implementation may require. Coupling 408 may be fabricateddifferently from coupling 410, e.g., by using a different fabricationmethod, superconducting material, sections, sizes, clearances, spans, orsome combination thereof.

With reference to FIG. 5, this figure depicts a simulation result fromusing a coupling resonator in accordance with an illustrativeembodiment. Configuration 400 of FIG. 4 is used in the simulation. Ane-field simulation at resonance confirms that coupling resonator 404together with couplings 408 and 410 does not interfere with anapproximately 2.07 e+02 dB field, which is generated by a 4.75 Gigahertz(GHz) signal on line 402 from qubit 102. In other words, couplingresonator 404 together with couplings 408 and 410 does not distort thefield in any significant way.

With reference to FIG. 6, this figure depicts another simulation resultfrom using a coupling resonator in accordance with an illustrativeembodiment. Configuration 400 of FIG. 4 is used in the simulation.

An e-field simulation at resonance confirms that coupling resonator 404together with couplings 408 and 410 does not distort or cause a loss inan approximately 1.15 e+02 dB field, which is generated by a 5.2 GHzsignal on line 202 from qubit 102A.

With reference to FIG. 7, this figure depicts another simulation resultfrom using a coupling resonator in accordance with an illustrativeembodiment. Graph 700 demonstrates that the magnetic cross-talk betweencoupling resonator 404 together with couplings 408 and 410, and crossedcomponent 402 is well below an acceptable threshold of −50 dB under twodifferent measurement setups.

With reference to FIG. 8, this figure depicts a set of equations tocompute a number of jumps needed in a lattice in accordance with anillustrative embodiment. Set 800 of equations assumes a square lattice,each side of the lattice having N qubits. Set 800 provides the number ofjumps J that will be needed in the lattice. Specifically, J comprises anumber of coupling resonators (assuming that corresponding couplings forpotential ground plane equalizations are included with the couplingresonators) that are needed in the lattice such that no non-peripheralqubit requires a 3D fabrication of a line.

Various embodiments of the present invention are described herein withreference to the related drawings. Alternative embodiments can bedevised without departing from the scope of this invention. Althoughvarious connections and positional relationships (e.g., over, below,adjacent, etc.) are set forth between elements in the followingdescription and in the drawings, persons skilled in the art willrecognize that many of the positional relationships described herein areorientation-independent when the described functionality is maintainedeven though the orientation is changed. These connections and/orpositional relationships, unless specified otherwise, can be direct orindirect, and the present invention is not intended to be limiting inthis respect. Accordingly, a coupling of entities can refer to either adirect or an indirect coupling, and a positional relationship betweenentities can be a direct or indirect positional relationship. As anexample of an indirect positional relationship, references in thepresent description to forming layer “A” over layer “B” includesituations in which one or more intermediate layers (e.g., layer “C”) isbetween layer “A” and layer “B” as long as the relevant characteristicsand functionalities of layer “A” and layer “B” are not substantiallychanged by the intermediate layer(s).

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “illustrative” is used herein to mean “serving asan example, instance or illustration.” Any embodiment or designdescribed herein as “illustrative” is not necessarily to be construed aspreferred or advantageous over other embodiments or designs. The terms“at least one” and “one or more” are understood to include any integernumber greater than or equal to one, i.e. one, two, three, four, etc.The terms “a plurality” are understood to include any integer numbergreater than or equal to two, i.e. two, three, four, five, etc. The term“connection” can include an indirect “connection” and a direct“connection.”

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedcan include a particular feature, structure, or characteristic, butevery embodiment may or may not include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

The terms “about,” “substantially,” “approximately,” and variationsthereof, are intended to include the degree of error associated withmeasurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of ±8% or 5%, or 2% of a given value.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdescribed herein.

What is claimed is:
 1. A superconducting coupling device comprising: asuperconducting coupler comprising a superconducting connection betweena first superconducting device fabricated in a plane and a secondsuperconducting device fabricated in the plane, wherein a section of thesuperconducting coupler lies in a parallel plane at a clearance from theplane; a first ground plane on a first side of a component of the secondsuperconducting device, wherein the clearance at least equals athreshold clearance, and wherein an insulator is formed between thecomponent and the superconducting coupler to create the clearance; asecond ground plane on a second side of the component of the secondsuperconducting device; and an equalizing structure, wherein theequalizing structure equalizes a potential of the first ground planewith a potential of the second ground plane.
 2. The superconductingcoupling device of claim 1, wherein the superconducting couplercomprises a resonator, and wherein the resonator is formed using awirebond.
 3. The superconducting coupling device of claim 1, wherein thesuperconducting coupler comprises a resonator, and wherein the resonatoris formed using a coplanar waveguide.
 4. The superconducting couplingdevice of claim 1, further comprising: a ground plane coupling betweenthe first ground plane and the second ground plane.
 5. Thesuperconducting coupling device of claim 4, wherein the ground planecoupling is a superconducting coupling.
 6. The superconducting couplingdevice of claim 4, wherein the ground plane coupling is asuperconducting coupling, wherein the superconducting coupler comprisesa superconducting resonator, and wherein a shape and a material of thesuperconducting resonator and the superconducting coupling are same as ashape and a material of the superconducting resonator.
 7. Thesuperconducting coupling device of claim 1, further comprising: a risingsection of the superconducting coupler, wherein the rising sectioncouples one end of the superconducting coupler to one section of thesuperconducting connection on the first side of the component; and arejoining section of the superconducting coupler, wherein the rejoiningsection couples a second end of the superconducting coupler to thesecond section of the superconducting connection on an opposite side ofthe component.
 8. The superconducting coupling device of claim 1,wherein the first superconducting device is a first qubit, wherein thesecond superconducting device is a second qubit, wherein thesuperconducting connection of the first superconducting device is a readline of the first qubit, and wherein the component of the secondsuperconducting device is a resonant line of the second qubit.
 9. Amethod comprising: forming a superconducting coupler comprising asuperconducting connection between a first superconducting devicefabricated in a plane and a second superconducting device fabricated inthe plane, wherein a section of the superconducting coupler lies in aparallel plane at a clearance from the plane; forming a first groundplane on a first side of a component of the second superconductingdevice, wherein the clearance at least equals a threshold clearance, andwherein an insulator is formed between the component and thesuperconducting coupler to create the clearance; forming a second groundplane on a second side of the component of the second superconductingdevice; and forming an equalizing structure, wherein the equalizingstructure equalizes a potential of the first ground plane with apotential of the second ground plane.
 10. The method of claim 9, whereinthe superconducting coupling device comprises a resonator, and whereinthe resonator is formed using a wirebond.
 11. The method of claim 9,wherein the superconducting coupling device comprises a resonator, andwherein the resonator is formed using a coplanar waveguide.
 12. Themethod of claim 9, further comprising: forming, as a part of forming thesuperconducting coupling device, a ground plane coupling between thefirst ground plane and the second ground plane.
 13. The method of claim12, wherein the ground plane coupling is a superconducting coupling. 14.The method of claim 12, wherein the ground plane coupling is asuperconducting coupling, wherein the superconducting coupling devicefurther comprises a superconducting resonator, and wherein thesuperconducting resonator and the superconducting coupling are formedusing different superconducting materials.
 15. The method of claim 9,further comprising: forming a rising section of the coupling resonator,wherein the rising section couples one end of the coupling resonator toone section of the superconducting connection on the first side of thecomponent; and forming a rejoining section of the superconductingcoupling device, wherein the rejoining section couples a second end ofthe superconducting coupling device to the second section of thesuperconducting connection on an opposite side of the component.
 16. Themethod of claim 9, wherein the clearance at least equals a thresholdclearance, and wherein an insulator is formed between the component andthe superconducting coupling device to create the clearance.
 17. Themethod of claim 9, wherein the first superconducting device is a firstqubit, wherein the second superconducting device is a second qubit,wherein the superconducting connection of the first superconductingdevice is a read line of the first qubit, and wherein the component ofthe second superconducting device is a resonant line of the secondqubit.
 18. A superconductor fabrication system comprising a lithographycomponent, wherein the superconductor fabrication system when operatedon a die to fabricate a superconductor device performs operationscomprising: forming a superconducting coupler comprising asuperconducting connection between a first superconducting devicefabricated in a plane and a second superconducting device fabricated inthe plane, wherein a section of the superconducting coupler lies in aparallel plane at a clearance from the plane; forming a first groundplane on a first side of a component of the second superconductingdevice, wherein the clearance at least equals a threshold clearance, andwherein an insulator is formed between the component and thesuperconducting coupler to create the clearance; forming a second groundplane on a second side of the component of the second superconductingdevice; and forming an equalizing structure, wherein the equalizingstructure equalizes a potential of the first ground plane with apotential of the second ground plane.
 19. The superconductor fabricationsystem of claim 18, wherein the superconducting coupling devicecomprises a resonator, and wherein the resonator is formed using awirebond.
 20. The superconductor fabrication system of claim 18, whereinthe superconducting coupling device comprises a resonator, and whereinthe resonator is formed using a coplanar waveguide.
 21. Thesuperconductor fabrication system of claim 18, further comprising:forming, as a part of forming the superconducting coupling device, aground plane coupling between the first ground plane and the secondground plane.
 22. The superconductor fabrication system of claim 21,wherein the ground plane coupling is a superconducting coupling.
 23. Thesuperconductor fabrication system of claim 21, wherein the ground planecoupling is a superconducting coupling, wherein the superconductingcoupling device further comprises a superconducting resonator, andwherein the superconducting resonator and the superconducting couplingare formed using different superconducting materials.
 24. Thesuperconductor fabrication system of claim 18, further comprising:forming a rising section of the coupling resonator, wherein the risingsection couples one end of the coupling resonator to one section of thesuperconducting connection on the first side of the component; andforming a rejoining section of the superconducting coupling device,wherein the rejoining section couples a second end of thesuperconducting coupling device to the second section of thesuperconducting connection on an opposite side of the component.